What a mad thread! But strangely compelling. Am sure it'll be read by some poor marketing sod trying to figure out the "mumsnet demographic"...
I like to think I'm not a brand-y type but thinking about it there are some brands I'm slavishly quite loyal to. I just figure if there's something I like, that works, that suits me and my crazy sensitive skin then why try and find something else [lazy emoticon].
Clothes:
converse
birkenstocks
Du Pareil Au Meme clothes for my baby son (I just love their stuff but can only get it when I visit family back in Ireland).
Home/laundry:
Ecover non-bio, fabric softener, handsoap and multipurpose cleaner (I heart ecover and have been using these products since about 1997!)
bio-D nappy powder
bumgenius reusable nappies.
Food/drink:
Barrys tea (when I can get it, cafe direct if not)
weetabix
Flahavans oats
Kelloggs cornflakes (I'm particular about cereal
)
Total greek yogurt.
Toiletries:
Aveeno face moisturiser
Clinique happy or happy heart perfume
Origins hand cream
Aveda hang straight and be curly (depending on whether I want to fight my curly hair or embrace it 
)
mitchum deodorant.
Cars: Toyota or VW (we have a golf but hire a prius whenever we can on holidays!)
Computery stuff: Apple (for both macbook and iphone), Google, wordpress.